Cohtrol system



Nov. 29, 1927.

" H. G. GEISSINGER CONTROL SYSTEM Filed Jan. 14. 1924 2 Sheets-5heet 1 "Nov. 29, I927. r 1,650,623

' H. G. GEISSINGER CONTROL SYSTEM Filed Jan. 14, 1924 2 Sheets-Sheet 2 //6// .38 58 Lou/- wmf MA.

Patented Nov. 29, 1927.

UNITED STATES HARRY G. eEIssrNGnR, 0F DETROIT, MICHIGAN.

CONTROL SYSTEM.

Application filed January 14, 1924. Serial No. 686,157.

The invention relates to a system for antomatically controlling the temperature in .a furnace by automatically regulating the heat'input thereinto and consists in a novel method of electrically connecting the standard types of temperature indicating and recording apparatus with other standard types of apparatus for increasing or diminishing the heat supplied to the furnace.

In the present state of the'art it is usual to obtain control of gas and oil fired furnaces by means of an automatic valve which has two positions of adjustment, one for supplying excess fuel over that required to maintain the furnace at a=predetermined temperature and the other for supplying too one of the objects of the invention is to provide a relay which will automatically open the maximum heat input circuit should the; relay fail from any reason such'as the interruption of-the power circuit Orother electrical defect. Relays, which have. heretofore been used for this purpose, have been mechanically locked in one'of the twoposi tions and if de-energized or defective will remain at last set, leaving the heat-input full on or off as may happen. 'W'ith my apparatus, however, any defect in the opera- 'tion of the apparatus always places the valve in the position corresponding to the minimum heat input.

Another object of the invention is to obtain an apparatus which may be connected to commercial line voltages and at the same time provide only a-small difference of potential when transferring from the high to the low contact.

A further object of the invention is to provide an arrangement .rhicn permits manual control of the heat input which is espccially important if the instruments are segregated at considerable distance from the furnace.

These and other objects are accomplished by my novel arrangementof circuits herein-- after more fully described;

In the drawings Figures 1 to 3 illustrate the electrical connections of the control system when used with a volt meter type 'ofithermometric instrument, Figure 1 showin the circuit when the low contact is close ,Figure 2 show-,

and 8 show thec ircuitswhen the,

thermocouple is in control; Y i In general my system comprisesa controlling circuit for .the heatlinpnt .me'chanism opened and, cl'osed vb y a relayiwhich is elec-ltrica-lly .connecte dgtoithe high? and-flow? contacts upon the 4 thermometric. instrument-, The relay is -normally.-connectediin-a circuit of high resistancelsuch asv to.- allow a small.

current to. energiaeithe rela'y sufiicielitlytomaintain the samejrnclosed,position butin suflicient to actuate ,the same. from openiato closed positionffl,- The;circui ts fbet w'enj the low, and high. contacts andthe relay are so arranged that .when. the flow? contact ill.-

made, part of thej resistancein the cir tuit l is shorted, thereby allowing a large current to pass through the relay which is sufficienti to close the same if it ha pens to be in open position. When thelfhigh 3, contact is.made,. the circuits arearran'ged tqslllll ltarou ndthe relay, thereby; entirely. deenergizing same and causing" it to ,open the controlling circuit. Thus rhi.1 1ay- ;saim sjn one-of- '1 tlle h at in ut mechanism 1 is represented as comprising a valve 2 adapted to Open and close the passage through a fuel conduit 3 and this valve is controlled by the energization of an electro-magnet 4 in the main circuit A manually operable switch 6 is arranged to control the circuit 5 and has three positions of adjustment corresponding to the contacts 7, 8 and 9. \Vhen the switch is placed on the contact 9 the circuit 5 is closed, thus energizing the magnet 4 and opening the valve 2 while moving the switch to contact 7 opens the circuit 5 and thereby closes the valve 2. The third position of the switch 6 is for the purpose of automatic control and thus when the switch arm 6 contacts at 8 the circuit 5 is either opened or closed depending upon the position of the switch 10 actuated by the relay 11.

The relay 11 is normally connected in a circuit including a resistance 12 and 21 separate resistance 13, these resistances being of such a value that a small current flows through the relay, this current being insufiicientto close the relay if in the open position but being sutiicient to prevent the opening of the'relay if it is in closed position. 14 and 15 are the low and'high eontactsrespectively of the thermometric instrument- 16 and are connected to opposite sides of the relay 11' by conductors 17 and 18. A cooperating contact 19 relatively movable with respect to the low and high conmess" is electrically connected to the resistance '12 by a conductor 20 and is so arranged that when'contact is made with the low contact'as shown in Fi urel theresist-ance 12'is"s'hort' circuitedan the relay 11 is energized b a 'lar er current sufficient to close the 10', t e direction- "offl0w of this current being indicated by the arrows.

Figure 3 i lus'trates the-current How in the circuitswhen the high contact 15 is en gaged by the cooperatinw contact 19, this arrangeinent short circnitingboth the resistance '12 and the relay 11, thereby opening the switch 10 and breaking the controlling circuit 5. i

It has been stated that my control system can be used with different t 'es of thermometri'c instruments and in igures 1, 2 and 3'it is shown as being connected to a volt meter typeof instrument, this; of course,

being shown only diagrammatically in the drawings. *As showm however, 21 indicates a thermocouple suitably connected to a galvanometer coil 22' for rotating the, pointer 23 about a pivot 24, the position of the pointer depending upon the temperature of the thermocouple. Instruments of this type are usually provided with a depressor bar 25 which is intermittently actuated by suitable mechanism, not shown, to bearagainst the pointer 23 and if the pointer is within the range of the contacts 14 and 15 the circuits illustrated in Figures 1 and 3 will be completed. Vhen, however, the depressor bar 25 is not. bearing against the pointer 23 neither the resistance 12 nor.the relay 11 are short circuited and the current flows through the relay as illustrated in Figure 2 and the relav remains in its last position of adjustment. Figure 2 shows the switch 10 in closed position, therefore indicating that in the last previous operation of the depressor bar the therinometric instrument was upon the low side of a predetermined temperature. It- \\'ill be understood, of course, that the low and high contacts are adjustable on the instrument to correspond with any predetermined temperature within the range of the instrument.

In order to insure that the heat input will be a minimum, if for any reason the electrical connections of the thermocouple become broken. there is provided a contact 26 in the path of the pointer 23 corresponding with the zero reading of the instrument. This contact is electrically connected with the high contact 15 so that if the pointer assumes the zero position'the relay 11 will be short circuited in the same manner as shown in Figure 3 and the control circuit 5 will, therefore, be opened. 5

Since'it is the usual practice in the voltmeter type of instruments to make the range of temperature covered by thelow and high contacts quite narrow there is considerable range of temperature below the i low contact. In order to start the furnace when the instrument is within this temperature range there is provided a starting key 27 which, when depressed, causes the re sistance' 12 to be short circuited and thus closes the control circuit 5;

In Figure et'there is illustrated the elec trical connections for applying my system ti) a 'potentiometer'type instrument commonly lmown as a single point recorder. This instrument, as diagrammatically illustrated, has high and low contacts 28 and 29, respectively upon a ring 30 mechanically actuated by suitable mechanism, not shown; It will be understood that the rotat-ivc posi tion of the ring is determined by the temperature of the thermocouple 31. The high and low segments are connected to the terminals 18 and 17 by the flexible connections 32 and 33 respectively, while they are insulated from each other at the opposite ends 34 and 35. A cooperating contact point 35 engages the ring and is electrically connected to the terminal 20. In this type of instrument it will be noted that the high and low contacts are movable. corresponding to the temperature of the thermocouple, 'lille the cooperating contact 36 is stationary but the operation of the heat input mechanism and its controlling circuit 5 is exactly the same as described above with the volt met-er type of instrument; It is the custom' to separate the extreme ends of the low-and high contact rings by a wide insulator-as shown at and thisinsulator ordinarily covers a range of temperature often reached when a heavy load is introduced into' ahot furnace. It will be noted,how'e\ier, that-even when the contact- 36hears againstthe insulator there is still "sufficient currentthrough the relay to maintain thesame in closed position, thereby allowing the maximum heat input.

In Figures 5 to 8 my system is sho'wn'-fas applied to a two point recorder which is sometimes used for indicating the temperat-ure both of the furnace proper and the muf-- fle within which the work'is placed. "Such instruments are provided 'with two separate rings such as show1i"at =37- and 38', each of which is provided with high and low contact ing segments insulated from each other; Inthese drawings 39 represents theth'ermocou ple located in the furnaceproper an'dcon trols the rotation 'ofthering' 38 -whilethe thermocouple 40 indicates the temperature of the mufile of the furnaeand controls the position of the ring 37i' 4'1' 'and42 jare thecooperating contacts respectively fb'earin'g against the rings 38 and 375 and are rese tively connected to the" brushes 43? and bearing against a commutator rin 'g ktfi a'ctu} ated by suitable timing" *ineehanisrhg 'nov shown. It will be'u'ndei'sto'odthatf; y the rotation of the commutator ring '45 the i'iiigs' 37 and 38 are-alternately 'c'onnebted' toithe' resistance 12 by means'of th'ontluctor iti and the conducting portion 47 lth'e can; mutator ring. The high fa'iid lo'ye cdrr tacts 48 and 49 of the 'mi'ifile "ring 37 a1 spectively connected to the terminalsT iiiid 17 The liigh.contact 50of"the' furnace ring is connected'to the highi conta 't 48" of the muffle ring, while-the-lowlfcoritacfi 51 of the furnace ring '38has no'other electrical onnection i I v 11? Jul t' l In Figure 5 the position ofthe' rings 3?"* and 38 indicate snb norniar"temperature (if both the furnace and-thef inufll'e' and since the commutator 45 is sh'own'connectingftlie' mufiie ring to the relay ci'rc'uit it"i'sf'vlden't that the resistance '12 will besh-drt'cirduited as shown by the arrows and'the heat inputwill; therefore, be at the maxin uirnj when the commutator breaks thecont'rol oftlie'inufF' fie ring 37 the relaywillstilljrmain in the same position due to'the small-energizing currentpassing'through 'tl'ie-re s'ista c 12.

Figure 6 illustratesthecircliits whcuthe muffle and the furnace are both above the predetermined temperature and itwiIllic evident that with the commiitatoif' lhf con necting either the furnace ring or the. mutrle ring the relay will be de-energized and they heat input placed at the minimum; InjIiig ures 7 and 8 the mufiie temperature is shown peratureshOuld' neVer he' allowed to rise to an appreciableextent above the limit set.

It -will be understood that-the'two point recorder? as diagrammatically illustrated in Figures?) to 8 is a standardinstrumentand in order to operate my system for muffle furnace controhit'is only necessary to connect the high fcontact segments together and then connect theinstrument to the=relay as illustrated in' the-drawings One other conditionofthe two pointjrecorder should be explainedg- 1 na mely, when the I furnace tenrperatuie ishbm-"e-the limit :set while the muflle-"temperature is still below the desired range-From-Fi'gure 6, it will beapparent t-hat'with this conditioir the relay llwvill be open forhalfofi the time and closed for the ot-herhalf, {this resulting in half-time maximum heat input until the furnace temperature 'has been reduce-dot the mufile tem: perature increased to the desired range. "If at any time it is desirable-{t6*control the hea'tinput from the muflle temperature alone will= only be necessary 'to' disconnect the Contact 41] v bearing against the furnace ring 38%"andfl-"tli'e ap aratus will still properly function {for the mufile ring'. Froi'n the above description it' will be ap-l parent that improved system'of furnace control may be applie d to variou's t'ypes of th'ermome'tric instrument-s but in; all of' the various-hookups one impbrtantfeature will be noticed, namely-, that the heat 'input'mech-- anism iso'nly adjusted when going-from the high? contact'to the 10w Contact or vice vers'a and the intermittent breakingof the contacts has no elfect'upon the mechanism; Fiirtliermore the is stem provides means for auton'iatica-lly placing the heat input mechn'ism in the minimum'positiondf any break age occurs in the 'thermocoupleconnect-ions or if there'is'hny 'failure in the actuating current'ffrom anyreason;

"NVhat'I claimi as my inye'ntion is 'IiZIn control system; the 5 combination with an electri'cal 'c'onti'fiol. [circuit 'and tenr perat'ure responsive meansfof l a relay for opening and closing saidcontrolcircuit normally'connecte'd in a circuit-marrying a predetermined currentsutficient to maintain said relay in closed'positionbut insuliicient to actuate the same, and nieans for' passing a larger or smaller current through said relay dependent upon the position of said temper'ature responsive means above or below a predetermined temperature.

2. In a control system, the combination with means for controlling the heat input and temperature responsive means, of a relay for actuating said heat input control means normally connected in a circuitin cluding an auxiliary resistance such as to allow an energizing current through said relay insufficient to actuate the same but sufiicient to prevent the release thereof. and electrical connections adapted to be completed when. said temperature responsive means is above or below a predetermined temperature for increasing or diminishing the amount of current through said relay.

3. In a temperature control system, the combination with temperature responsive means and an electrical control circuit. of a relay for opening and closing said circuit normally connected in a second circuit having an auxiliary resistance such as to cause continuousenergization of the relay with a currentof relatively low value, and electrical connections between said relay and saidE temperature responsive means arranged to cause a relatively large current through the relay when the temperature responsive meansis on one side of a predetermined temperature and to short circuit said relay when on the opposite side of said temperature.

4;. In a temperature control system, the combination with a furnace, a heat input mechanism having maximum and minimum positions of adjustment, and athermometric instrument having high and low contacts, of a relay for actuating said heat input mechanism connected to said high and low, contacts to energize said relay upon the making of one contact and de-energize the same upon the making of the other contact, and electrical means for maintaining said relay in the last position of adjustment when-neither contact is functioning.

5. In a temperature control system, the combination of a relay for opening and closing an electrical control circuit, a temperature indicating device, cooperating contacts mounted on said device adapted to alternately-complete one circuit on one side of a predetermined temperature and another circuit on the opposite side thereof, said cir cuits being arranged to respectively open and close said relay, and a normally closed circuit including said relay for continuously maintaining an energizing current in said my lay when both of the circuits completed by said contacts are inoperative.

6. In a temperature control system. the combination with an electrical control circuit and a temperature responsive means, of a relay adapted to open and close said control circuit, said relay being normally connected in a circuit having an. auxiliary resistance such as to slightly energize said re.- lay, means operated by said temperature responsive means when on one side of a pre determined temperature for shunting out said auxiliary resistance to strongly energize said relay, and means operated when on the opposite side of said temperature for shunting out said relay to deenergize the same.

7. In a temperature control system, the combination with a heat input mechanism having maximum and minimum positions of adjustment, and a thermometric instrument having high and low contacts, of a re lay for actuating said heat input mechanism normally connected in a circuit having an auxiliary resistance, electrical connections between said relay and said low and high contacts adapted to alternately complete circuits for respectively energizing and deenergizing said relay, and astarting switch for energizing said relay when the circuits through said high and low contacts are inoperative.

8. In a. temperature control system, the combination with an electrical vcontrol circuit and temperature responsive means,- of a relay for opening and closing said control circuit, a manually operable switch adapted to selectively energize said control circuit, de-energize the same and connect said relay in a circuit carrying a predetermined current sufficient to maintain said relay in closed position but insufiicient to actuate the same, and means for passing a larger or smaller current through said relay dependent upon the position of said temperature responsive means above or below a predetermined temperature.

9. In a temperature control system, the combination with a-furnace, a heat input mechanism having maximum and minimum positions of adjustment, and a thermometric instrument having high and low contacts to energize said relay upon the making of one contact and de-energize thesame upon the making of the other contact, electrical means for maintaining said relay in the last position of adjustment when neither contact is functioning, and a manually operable switch for disconnecting said relay and plac- 7 ing said heat input mechanism in maximum or minimum position according to the position of said switch regardless of the last previous position of adjustment.

10. In a temperature control system, the combination with a furnace, means for regulating the heat input thereof, a pair of thermocouples arranged in different locations in said furnace, and a thermometric instrument having movable members automatically adjustable to correspond to the temperatures of said thermocouples, of control means for said heat input mechanism having a high and a low circuit, a contactin device closed by one of said movable mem ers and arranged in said high circuit, a second contacting device closed by the other movable member and arranged in said high circuit, and a mechanically driven commutator adapted to intermittently complete the high circuit through one of said contacting devices When one of said thermocouples is above a predetermined temperature, said 10 commutator also serving to complete said low circuit when said thermocouple is below said predetermined temperature.

In testimony whereof I aflix my signature.

HARRY G. GEIS SINGER. 

